Another thought - if you meant to ask how to restore a window after minimizing it to the dock with cmd-M (rather than hiding the app with cmd-H), there's an even less well known shortcut: Open the command-tab switcher, select the app you want, then hold down option and release command.

Doesn't handle multiple windows gracefully (if the app has another window not minimized it won't do anything, just switch to that window as normal). But if you have an app with a single window and you've minimized it, this will pop it back up.

Alternatively, you can access the whole dock directly with a keyboard shortcut using ctrl-F3 (add Fn if needed depending on your keyboard setup).